Finished basements are great for homeowners who need a little extra living space or storage space. Whether you’re still in the planning stages or ready to start renovations, it’s important to keep insulation at the forefront of your mind. Without proper lining and protection, your newly designed space could become a money pit with moisture, mold, and mildew problems—just to name a few.

Many contractors recommend polystyrene boards for the lower levels of your home because they are particularly effective in protecting against moisture that comes with humidity, rain, and snow. You can keep your family and your wallet safe by following these steps for installing polystyrene boards as a proper layer of defense against the elements your home faces.

Step 1 – Protect Yourself

Before you begin any insulation work on your home, make sure to put on protective eyewear and work gloves to prevent injuring your hands or eyes. If possible, enlist the help of a family member or friend so that you aren’t going through the installation process alone. This will get the work done faster and protect you from unnecessary injuries.

Step 2 – Inspect the Space

Examine your entire basement for any moisture issues or cracks in the concrete. You don’t want to start an insulation project only to find there are more severe issues with your foundation. If you detect any problems, contact a certified contractor and schedule an appointment to have your basement assessed.

Step 3 - Protect your Walls

Once any moisture issues have been solved, you’ll need to apply a concrete sealant on the walls.

Visit your local hardware store, and speak with a customer service representative in the paint department about your project in order to get product recommendations. After you’ve selected a sealant you think will work well, open all the basement’s windows to ensure fresh air and healthy ventilation.

Apply the sealant using a paint roller, allowing the sealant ample time to dry. Some homeowners choose to apply a second coat to the walls for safe measure.

Step 4 - Buy Insulation Materials

Before you can buy the insulation for your basement project, you’ll need to take proper measurements of your walls. This will determine how much polystyrene board material you need to purchase.

Use a measuring tape to find the exact height, width, and depth of each wall. Once you have the measurements, you need to multiply the height and width to determine how much surface area needs coverage for each wall. Multiply each wall together to get your total surface area. Most polystyrene boards come in 4’x8’ slabs that you can buy at your local hardware store, so you’ll need to determine how many boards are needed to cover your entire calculated surface area. The thickness of these boards will vary, so you’ll need to make your selection based on the depth of your walls.

If you’re uncertain about your needs, you can always bring your measurements to your local home improvement store and talk to a representative. An associate will be able to tell you how many boards of polystyrene board insulation you will need to adequately cover your entire basement.

Be sure to pay attention to each brand and type for the R value, which will determine the efficiency of the product—the higher the R value, the more efficient the product.

Don’t forget that you’ll also need to purchase a foam board adhesive that works on cement and duct tape to secure the boards during installation.

Step 5 -Install the Insulation Boards

Apply the adhesive to the backside of the insulation board and press it firmly against the wall. You'll want to hold the piece in place for about a minute to properly secure it to the wall. You may need to use a saw to cut pieces down and shape them for small, obscure spaces.

Continue until all of the wall space has been covered. Apply duct tape over the seams between all of the boards to prevent any moisture from leaking in or to prevent any heated air from leaking out.

Step 6 - Frame your Walls

When all of the basement walls have been covered with polystyrene board insulation, use your hammer and concrete nails to secure spruce planks against the walls around the perimeter of the floor. The size of these planks will vary depending on the size of your walls. This will keep any moisture in the floor from moving up through the walls.

Continue to secure planks horizontally moving up the all to build a wall frame spaced approximately 16 inches apart. You can use a pencil or chalk to measure out evenly spaced lines to simplify the installation process.

You will then install planks vertically spaced approximately 16 inches apart. Make sure to start on one side of your wall and move to the other; do not start in the middle of the wall.

Note: By installing planks on top of each other and building the wall outward like this, you leave space for any necessary electrical wiring.

Step 7 – Finish your Basement

Now that your basement polystyrene board insulation is installed, you can add electrical work, drywall, paint, wallpaper, etc. The final touches for finishing your basement are up to you!